Starting out with ROS

This is going to be a pretty short post with the purpose of motivating future posts on related subjects.

I've got a lot of really cool robotics equipment now; a stock Hexy, a Cyclone Quadrotor, a Kinect, and a MakerBot Thing-O-Matic top the list, at the moment.

Unfortunately, a lot of these pieces of Hardware come with relatively  little software behind them. Hexy, for instance, has the short-but-sweet PoMoCo software to start. PoMoCo is great, but it's not very functional; by default, it allows only for interpolation between pre-programmed sequences of joint angles. It's very easy to pick the wrong combination of moves and get Hexy stuck in some contorted pose ( and you can forget about variable speed gaits ).

This isn't really PoMoCo's fault. Like Hexy, PoMoCo is designed to be a lightweight tool for beginners who can go on to use the platform for other things.

So, what's next for me on the Software side of Hexy? First off, I want to integrate Hexy with ROS (more on ROS in a later post). At first, I'm just going to hook PoMoCo into ROS and control it from the command line, but I plan on splitting PoMoCo into three ROS nodes, with the eventual goal of augmenting one of them with good gait generation and motor planning, and replacing the other with a series of ROS services to utilize Hexy from any ROS interfaced program.

In any case, I'll be working on Hexy when I  don't have to tool, and tooling when I can to get as much work in on Hexy. I'll keep you posted.

Voroni Diagrams and Graphs IV: Efficient Computation of the Graph and it's simplexes.

Before we jump into algorithms, a few things. The algorithm I'm about to lay out is a version of the Bowyer-Watson algorithm I've referenced in a previous post. It's been pretty heavily modified since, and it was not my initial intent for it to be thins similar. Nonetheless, I think that my implementation has better asymptotic time than any implementation of the original I've yet seen, since (as we'll see) the most intensive parts of the algorithm (most of which were related to searches over the point set) have been offloaded to a simple graph search. We'll also be looking at things through the lens of the Voroni Graph, rather than the Delaunay Triangulation.

A Simple 2D Graphics Engine Powered by OpenGL/GLUT.

In the course of coding up my ideas on the Voroni Graph, it became apparent that a CLI wasn't going to cut it. I needed some sort of graphical library, both for the final visualization, and for debugging. For this, I've chosen to use OpenGL with my own wrappers on top. This is a log of what I've been working on for the past few evenings.

This is, without the slightest doubt, overkill for what I'm doing right now (2D, very few colors, order of 100 different positions.). Screw that, I'm using OpenGL anyways. Why? I want the experience, and I want to write my own graphics engines that won't be limited by the underlying platform.

In any case, the process of getting to where I am now has been fairly frustrating. The documentation for all sorts of things involving OpenGL on the web is scant and often contradictory. Some things didn't work, other important aspects of a simple program had been depreciated. Getting even a blank screen to compile was a significant achievement.

In any case, this was all difficult enough to warrant a post and some preliminary code. Below is a sort of black box on the whole process, written as I worked through everything. For this reason, please excuse the weird tenses.